Figure 8.

An example of the final PDMS device as well as images of a fluorescent dye inside the device. (a) The actual final PDMS device as is used in experiments. (b) Presence of fluorescent dye in largest channel, nominally 0.8 μm, (c) Presence of fluorescent dye in smallest channel, nominally 0.3 μm. One observes that the dye is able to enter the growth channels. The inhomogeneity of the light intensity observed is due to the Gaussian profile of the laser beam. We performed a control experiment (data not shown here) by measuring the fluorescence signal in the absence of the fluorescent dye. During these conditions no significant fluorescence signal was detected in the trench or growth channels. This observation supports our conclusion that the signal detected as shown in the above images are due to the fluorescent dye in the trench and growth channels.